The present invention relates to coupling devices of the type used to transmit torque, for example, in a vehicle drive line, and more particularly, to an improved clutch assembly for use in such a coupling device, and an improved arrangement for providing lubrication to the clutch assembly.
As used herein, the term “coupling device” will be understood to mean and include a device which is able to transmit torque from an input to one or more outputs, and in which there is a clutch assembly disposed between the input and the output, such that the amount of torque transmitted is a function of the extent of engagement of the clutch assembly. Within the scope of the present invention, the term “coupling device” means and includes both gear-type devices (such as differentials), as well as gearless-type couplings, although it will be understood by those skilled in the art from reading and understanding the present specification, that the invention will probably find its greatest application in gear-type coupling devices, i.e., those including conventional differential gearing.
Although the coupling device and the improved clutch assembly for use therein, in accordance with the present invention, may be utilized with many different types and configurations of coupling devices, it is especially advantageous when utilized in conjunction with vehicle differentials of the type illustrated and described in U.S. Pat. Nos. 5,310,388 and 6,464,056, both of which are assigned to the assignee of the present invention and incorporated herein by reference. Both of the above-incorporated patents show differential coupling devices of the gear-type.
In the differential coupling devices of the cited patents, there is a clutch pack operable to transmit torque between the input (housing connected to the ring gear) and the output (one of the axle shafts), with the degree of engagement of the clutch pack being determined by the fluid pressure in a piston chamber. The fluid pressure biases a clutch piston against the clutch pack. The differential coupling devices of the cited patents include a gerotor pump having one rotor fixed to rotate with the input and the other rotor fixed to rotate with the output, such that the flow of pressurized fluid into the clutch piston chamber is generally proportional to the speed difference between the input and the output. As used herein, the term “clutch pack” will be understood to mean and include both a multiple friction disc type clutch pack, as well as any of the other well known types of clutch assemblies, such as cone clutches, in which the degree of engagement is generally proportional to the fluid pressure acting on the clutch piston, or on an equivalent clutch-engagement structure.
It should be understood that the present invention is not limited to any particular type of “clutch apply” arrangement, i.e., the clutch pack can, within the scope of the invention, be loaded or biased by some means other than a fluid pressure biased piston. In addition, the present invention is not specifically limited to a coupling device in which the source of pressurized fluid (if a pressure biased piston is used) is an “on-board” pump. The invention may also be used advantageously in coupling devices in which the source of pressurized fluid is some sort of pump external to the differential coupling device.
The present invention does find its primary application in differential coupling devices of the type in which the clutch assembly (clutch pack) comprises a multiple friction disk type clutch pack, in which every other disk within the clutch pack is rotatably fixed, relative to the housing of the coupling device, by some sort of “ear” arrangement. In such an arrangement, of the type which is now generally well known to those skilled in the art, the “eared disks” each have a plurality of half-circular ears (tabs) disposed about the outer periphery of the disk, while the adjacent clutch housing includes a corresponding number of ear-receiving devices, received within recesses or cut-out portions defined by the clutch housing.
More specifically, the ear-receiving devices have typically comprised members known as “ear guides” which have conventionally been stamped from cold rolled steel and then subsequently hardened, to be able to withstand the substantial torques transmitted from the housing, through the ear guides, to the eared disks, and eventually to the axle shaft. Although, in many differential devices, the use of such ear guides has been generally satisfactory, those skilled in the art have recognized that there is a substantial disadvantage in the need to use the separate ear guides, in terms of manufacturing costs and space within the coupling device.
It has also been observed that in differential coupling devices of the type shown in the above-incorporated patents, appropriate lubrication of the individual friction disks of the clutch pack can be quite difficult. It may be noted from a review of the above-incorporated patents that, in those devices, the clutch pack tends to be totally surrounded by housing and other associated structure, and very much isolated from a source of lubrication, which would typically be the fluid contained in a reservoir defined by the outer differential housing.